This invention relates to vascular catheters and in particular closed catheters for insertion into veins of patients especially those used for long term catheterization.
The terminal or hub of vascular catheters is generally sealed by a valve or septum. These valves or septa are generally accessed frequently by cannula (such as Luer cannula) or needles to infuse fluid or medication. Upon removal of the accessing cannula from the valve or septum there is commonly a slight negative pressure induced within the catheter which can draw small volume or blood into the catheter tip thereby inducing clotting. Such clot formation increases the infection risk, may induce propagation of thrombosis in the vein, and reduces the useful life of the catheter due to occlusion. U.S. Pat. No. 5,474,544 of the present inventor (the disclosure of which is incorporated by reference as if completely disclosed herein) shows a valve for inducing positive pressure upon withdrawal of a Luer cannula. Subsequently a variety of other positive pressure valves have since been introduced to solve this problem. These valves, especially those introduced subsequent to the issuance of my aforementioned patent, are complex and expensive. In addition, many of the recent positive pressure valves, in association with the increased mechanical complexity of the catheter hub, may add to the colonization risk of the catheter hub. Indeed the catheter hub region is an area which has been increasingly implicated as the source of potentially fatal bacteremia in needleless devices by the Center for Disease Control so it is difficult to suggest, in the interest of patient safety that further increases in the mechanical complexity of such hubs is warranted for any purpose. For these reasons these more complex xe2x80x9cpositive pressurexe2x80x9d valves may be simply exchanging one risk (catheter tip thrombosis) with another, more significant risk (catheter related bacteremia). It is important to reduce the mechanical complexity of any interface between the human vascular system and the environment. In addition conventional positive pressure valves add considerable expense.
The present invention solves the problem of terminal negative pressure upon cannula withdrawal by providing a positive pressure generator proximal the valve or septum for inducing sufficient positive pressure in the lumen or fluid path of the catheter so that a sufficient portion of the fluid at the tip of the catheter is forced into the blood vessel after the cannula or needle has been removed from the hub so that any blood in the tip is displaced back into the vessel or is sufficiently diluted such that clotting within the lumen adjacent the tip is substantially mitigated. The positive pressure generator is preferably comprised of a flexible tube or cavity which has a variable internal volume and which is configured to have a first stable configuration with a first internal fluid volume and a second stable configuration with a smaller internal fluid volume. The tube is configured such that it may be distorted, compressed, or flexed to decrease the volume within the tube during the change from the first configuration to the second configuration thereby forcing at least a portion of the volume of the fluid toward the lumen of the catheter. In one embodiment the tube is pleated with the pleats separated in a first configuration and advanced to intussusept each other in a second configuration the advancement inducing a reduction of the internal volume to cause fluid to flow toward the catheter lumen. In the presently preferred embodiment the a configuration changing member is provided about the tube. The member is preferably movable from a first position wherein the tube is in the first configuration to a second position wherein the tube is distorted into the second configuration. The member is preferably a clamp having opposing surfaces for compressing the tube along a length of the tube sufficient to induce a sufficient flow of fluid within the lumen of the tube toward the catheter lumen to cause displacement of blood out of the tip of the catheter, and further is preferably a peristaltic clamp sized and configured to be mounted with the tubing intermediate the catheter and the hub which can be a elongated slit clamp. The clamp is preferably comprised of resilient and flexible plastic and can include a lock for holding the clamp in the second position with the tube in the compressed position. In the preferred embodiment the clamp is configured to close so as to compress the more proximal portion of the tube first and then occlude the more distal portion so that fluid is propelled toward the vascular system. In one preferred embodiment the clamp is a peristaltic clamp positioned on the tube to progressively compress the tube toward the vascular system. This clamp includes a proximal portion, which occludes the proximal tubing portion first. Preferably the clamp, in the second position holds the clamped portion of the tube in a stable compressed configuration so that negative pressure cannot develop within the lumen of the tube. Alternatively the clamp may be configured to isolate the compressed segment from the proximal valve or septum.
It is the purpose of the present invention to provide a simple and inexpensive flow generator, which can flush blood from the lumen of a catheter and eliminate the need for complex positive pressure generating needleless valves at the hub.
It is further the purpose of the present invention to provide a method for flushing blood from the catheter tip which does not require modification of the needleless valve at the hub.
It is the purpose of the present invention to provide flow generator and method of generating flow which provides a closed fluid filled conduit system having a closed hub at one end and a catheter having an internal lumen extending to a opening at another end, the system having a first stable configuration defining a first internal volume and a second stable configuration defining a second internal volume, the second volume being sufficiently smaller than the first volume so that fluid is displaced toward the lumen and out the opening so that blood is flushed from the opening to prevent the blood from clotting within the lumen adjacent the opening.
It is further the purpose of the present invention to provide a positive flow generator which is free from contact with a luer tip so that infection risk can be reduced.
It is the further the purpose of the present invention to provide a catheter, and a closed hub, and a flexible cavity or tube intermediate the hub and the catheter, and a biasing member for biasing the tube or cavity into a configuration with a reduced volume thereby displacing fluid sufficient fluid into the catheter to flush blood from the distal end of the catheter lumen, the biasing member being free from direct contact with the fluid within the cavity or tubing so that the risk of contact contamination is reduced.
It is the further the purpose of the present invention to provide a catheter, a closed hub, a flexible tube intermediate the hub, and a clamp configured to compress a sufficient length of the tube to displace blood from the catheter lumen to prevent thrombosis within the lumen without inducing substantial negative pressure adjacent the hub.